1. Field of the Invention
This invention pertains to the field of nondestructive testing and in particular to the nondestructive testing of multilayer ceramic capacitors. Specifically, this method of nondestructive testing is directed to discovery of delaminations and nonvisible cracks in a ceramic capacitor body.
2. Description of the Prior Art
In the prior art, the testing of multilayer ceramic capacitors for either delaminations or nonvisible cracks has been primarily destructive testing. As the name implies, this testing is restricted to samples of a lot and consequently is not effective with respect to individual units within the lot. Though nondestructive testing has been suggested, however, few economically successful techniques have been developed to date. Among the proposed or attempted means of nondestructive testing, there have been at least four alternatives. Ultrasonic scanning is a form of bulk testing which to date has been unable to isolate individual defective units within a lot and consequently has not been very successful. Neutron radiography is a very complex and expensive means of testing but has not yet provided an adequate resolution. The scanning laser acoustic microscope provides a very expensive means of testing but it does rely on human judgment and is relatively slow. Testing by acoustic emission is a very slow process.
The delamination of the layers in a multilayer ceramic capacitor shortens the life of the device, significantly decreases its reliability and causes problems in soldering related to thermal expansion. The delamination of layers in a multilayer ceramic capacitor is not detected by the usual capacitance and resistance tests.